On Tue, Apr 28, 2015 at 04:43:00PM +0200, Takashi Iwai wrote:
> At Tue, 28 Apr 2015 15:05:20 +0200,
> Takashi Iwai wrote:
> > At Tue, 28 Apr 2015 13:35:18 +0100,
> > Jonathan McDowell wrote:
> > > On Tue, Apr 28, 2015 at 02:00:17PM +0200, Takashi Iwai wrote:
> > > > At Tue, 28 Apr 2015 12:21:57 +0100,
> > > > Jonathan McDowell wrote:
> > > >
> > > > > Having upgraded to 4.1-rc1 from 4.0 I'm now hearing audio
> > > > > crackles at regular intervals. I'm fairly sure this is due to
> > > > > the HDA power save as once audio is playing things are fine,
> > > > > it's just when starting to play audio that I hear the crackle.
> > > > > 
> > > > > System is a Dell Latitude E7240. I haven't tried a bisect yet
> > > > > but will attempt to find some time to do so in the next few
> > > > > days. It looks like there have been some changes in sound/hda/
> > > > > between 4.0 + 4.1-rc1 so I'll concentrate on those first.
> > > > > 
> > > > There are lots of code changes and enhancements wrt power saving
> > > > in 4.1, and bisection won't help so much, I'm afraid.
> > > > 
> > > > First off, check the device status while you hear crackles.  Is
> > > > the codec in runtime suspend (aka power save)?  This can be seen
> > > > in /sys/bus/hdaudio/devices/*/power/runtime_status.  Then check
> > > > the runtime status of the controller, too, found in
> > > > /sys/class/sound/card?/device/power/runtime_status.
> > > 
> > > The cracking is definitely happening with the transition from suspended
> > > to active:
> > > 
> > > /sys/class/sound/card0/device/power/runtime_status:suspended
> > > /sys/class/sound/card1/device/power/runtime_status:active
> > > /sys/bus/hdaudio/devices/hdaudioC0D0/power/runtime_status:suspended
> > > /sys/bus/hdaudio/devices/hdaudioC1D0/power/runtime_status:active
> > > 
> > > card1 + C1D0 were suspended, I hit delete in a terminal to force a
> > > terminal bell, got the crackle and the state changed to active as above.
> > 
> > Ah, so it's a click noise that happens only once per runtime PM
> > transition?  I thought it were constant crackling noises from your
> > description ("regular intervals").
> > 
> > In anyway, please give alsa-info.sh output on both 4.0 and 4.1.
> 
> Also, does the click noise occur only at powering up, and not at
> powering down?

The click is only on the transition from suspended to active; not
constantly during playback and not when transitioning from active to
suspended. It doesn't appear 4.0 is doing the suspending at all; there
are no /sys/bus/hdaudio/devices/*/power/runtime_status files and the
card runtime_status is always active. alsa-info for 4.0 + 4.1-rc1
attached.

J.

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